It didn't take a lot of horsepower to make the holes in which we set the explosives and hydrophones – just a water pump and a couple of guys with pipe wrenches. water was relatively easy to come by. In most cases the crew only had the dig a sump one or two feet deep and place the filtered end of the inlet hose into the sump. The pumps were simple single-cylinder Briggs and Stratton engines attached to a centrifugal pump. We pumped the water down a fire hose into a swivel screwed on the top of a thin-walled steel pipe. The guys would turn the pipe with the pipe wrenches to keep the pipe free while the water rushing down the inside of the pipe washed out the organic matter or sand and the base of the pipe and just washed it up the outside of the pipe. The water would return to the sump and be recycled.
No drilling fluids, no chemicals so nothing introduced to the ground except the explosives. Once the hole was flushed the charge would be primed with a detonator and set down the hole to the required depth. Of course, it took way longer to drill and set the charges than to pop them off so the drill crews were working ahead of the recording crews. They had a technique to set the detonator wire coil a little ways down the hole and secure it so the recording crews could recover it when it was time but so a casual passer by would struggle to do so.
And there were some passers by from time to time. After all, we were opening up all these foot paths into the normally inaccessible jungle.
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